Clinical evaluation of posterior flowable short fiber-reinforced composite restorations without proximal surface coverage.

The purpose of this clinical trail was to assess the clinical behavior of posterior composite restorations supported by a substantial foundation of flowable short fiber-reinforced composite SFRC (everX Flow, GC, Japan) used without proximal surface coverage with particulate filler resin composite (PFC). Seventy patients (20 males, 50 females; mean age: 30 ± 10 years) were randomly enrolled in this trial. Patients received direct restorations of either SFRC covered only on the occlusal surface (1-2 mm) by conventional PFC composite (G-ænial Posterior, GC), or plain conventional PFC composite without fiber-reinforcement, in Class II cavities in premolar and molar vital teeth. One operator made all restorations using one-step, self-etch bonding agent (G-ænial Bond, GC) according to manufacturers' recommendations. Two blinded trained operators evaluated the restorations at baseline, at 6, 12 and 18 months using modified USPHS criteria. Results indicated that, in both groups and at different follow-up intervals, according to evaluated criteria, restorations were rated mostly with best score (Alpha) (p > 0.05). For the marginal integrity after 6 months, a single case in the intervention [increased to 3 (8.8%) after 18 months] and 3 (9.7%) cases of the control group [increased to 4 (12.9%) after 18 months] had Bravo score but with no significant difference (p > 0.05). For color match measured after 6 and 18 months, three (8.8%) cases had Bravo score in the intervention group. The use of flowable SFRC composite without any PFC surface coverage proximally in Class II restorations demonstrated satisfactory clinical outcome throughout the 18-month follow-up.

Load-bearing capacity and wear characteristics of short fiber-reinforced composite and glass ceramic fixed partial dentures.

The aim of this study was to evaluate load-bearing capacity and wear performance of experimental short fiber-reinforced composite (SFRC) and conventional lithium-disilicate CAD/CAM fabricated fixed partial dentures (FPDs). Two groups (n = 12/group) of three-unit CAD/CAM fabricated posterior FPDs were made. The first group used experimental SFRC blocks, and the second group fabricated from lithium-disilicate (IPS e.max CAD). All FPDs were luted on a zirconia testing jig with dual-curing resin cement. Half of FPDs per group were quasi-statically loaded until fracture. The other half experienced cyclic fatigue aging (100.000 cycles, Fmax = 500 N) before loading quasi-statically until fracture. Fracture mode was examined using SEM. Wear test was performed using 15,000 loading cycles. Both material type and aging had a significant effect on the load-bearing capacity of FPDs. Experimental SFRC CAD without fatigue aging had significantly the highest load-bearing capacity (2096 ± 149N). Cyclic fatigue aging decreased the load-bearing capacity of the SFRC group (1709 ± 188N) but increased it for the lithium-disilicate group (1546 ± 155N). Wear depth values of SFRC CAD (29.3µm) were significantly lower compared to lithium-disilicate (54.2µm). Experimental SFRC CAD demonstrated the highest load-bearing capacity before and after cyclic fatigue aging, and superior wear behavior compared to the control material.

Wear behavior at margins of direct composite with CAD/CAM composite and enamel.

OBJECTIVES: The aim was to investigate the two-body wear at the marginal area between direct filling composites and substrate of CAD/CAM composites or enamel. MATERIALS AND METHODS: Flat specimens were prepared from CAD/CAM composites (CERASMART 270 and SFRC CAD) and bovine enamel. A box-shaped cavity cut into CAD/CAM composites and enamel surfaces was made. The prepared cavity in CAD/CAM composites was treated with a primer, while in enamel, the cavity was treated with an adhesive. Three conventional composites (Universal Injectable, G-aenial A'Chord, and Filtek Bulk Fill) and one short fiber composite (everX Flow) were placed and cured in the prepared cavities. A two-body wear test was conducted with 15,000 chewing cycles using a dual-axis chewing simulator. The specimens (n = 5/per group) were positioned to produce wear (load = 20 N) across the marginal area between filling composites and substrates. The wear depth was analyzed using a 3D optical profilometer. SEM was used to evaluate the wear behavior and margins between the filling and substrate materials. RESULTS: All composites used displayed different wear behavior (20-39 µm) (p < 0.05). The highest wear values were recorded for A'Chord and Filtek, while the lowest values were for Injectable and CERASMART 270. The data analysis showed that the wear behavior of substrate materials depends on the filling materials used at margins (p < 0.05). The marginal breakdown was seen only between bovine enamel and filling composites. CONCLUSIONS: The use of the two-body wear simulation method revealed important information about the behavior of the filling composites at the marginal area with CAD/CAM composites or bovine enamel substrates. CLINICAL RELEVANCE: The marginal breakdown related to the material combination at the bonding region.

Crack propensity of different direct restorative procedures in deep MOD cavities.

OBJECTIVE: The purpose was to evaluate the crack formation associated with different direct restorative procedures of the utilized resin composites (RC) right after and 1 week later of the restoration. MATERIALS AND METHODS: Eighty intact, crack-free third molars with standard MOD cavities were included in this in vitro study and randomly divided into four groups of 20 each. After adhesive treatment, the cavities were restored either with bulk (group 1) or layered (group 2) short-fiber-reinforced resin composites (SFRC); bulk-fill RC (group 3); and layered conventional RC (control). Right after the polymerization and a week later, crack evaluation on the outer surface of the remaining cavity walls was performed with a transillumination method utilizing the D-Light Pro (GC Europe) with the "detection mode." Between- and within-groups comparisons Kruskal-Wallis and Wilcoxon tests were used, respectively. RESULTS: Post-polymerization crack evaluation showed significantly lower crack formation in SFRC groups compared to the control (p<0.001). There was no significant difference within SFRC groups and non-SFRC groups (p=1.00 and p=0.11, respectively). Within group comparison revealed significantly higher number of cracks in all groups after 1 week (p≤0.001), however, only the control group differed significantly from all the other groups (p≤0.003). CONCLUSIONS: Post-polymerization shrinkage induced further crack formation in the tooth 1 week after the restoration. SFRC was less prone to shrinkage-related crack formation during the restorative procedure; however, after 1 week, besides SFRC, bulk-fill RC also showed less prone to polymerization shrinkage-related crack formation than layered composite fillings. CLINICAL RELEVANCE: SRFC can decrease the shrinkage stress-induced crack formation in MOD cavities.

Fatigue performance of endodontically treated molars reinforced with different fiber systems.

OBJECTIVE: The aim was to investigate the fatigue performance of root canal-treated (RCT) molars restored with different direct restorations utilizing discontinuous and continuous fiber-reinforced composite (FRC) systems. The impact of direct cuspal coverage was also evaluated. MATERIALS AND METHODS: One hundred and twenty intact third molars extracted for periodontal or orthodontic reasons were randomly divided into six groups (n=20). Standardized MOD, regular cavities for direct restorations were prepared in all specimens, and subsequently, root canal treatment and root canal obturation was carried out. After the endodontic treatment, the cavities were restored with different fiber-reinforced direct restorations as follows: SFC group (control), discontinuous short fiber-reinforced composite (SFC) without cuspal coverage (CC); SFC+CC group, SFC with cuspal coverage; PFRC group, transcoronal fixation with continuous polyethylene fibers without CC; PFRC+CC group, transcoronal fixation with continuous polyethylene fibers with CC; GFRC group, continuous glass FRC post without CC; and GFRC+CC, continuous glass FRC post with CC. All specimens underwent a fatigue survival test in a cyclic loading machine until fracture occurred or 40,000 cycles were completed. The Kaplan-Meier survival analysis was conducted, followed by pairwise log-rank post hoc comparisons between the individual groups (Mantel-Cox). RESULTS: The PFRC+CC group was characterized by significantly higher survival compared to all the groups (p < 0.05), except for the control group (p = 0.317). In contrast, the GFRC group showed significantly lower survival compared to all the groups (p < 0.05), except for the SFC+CC group (p = 0.118). The control group (SFC) showed statistically higher survival than the SFRC+CC group (p < 0.05) and GFRC group (p < 0.05), but it did not differ significantly from the rest of the groups in terms of survival. CONCLUSIONS: Direct restorations utilizing continuous FRC systems (in the form of polyethylene fibers or FRC post) to restore RCT molar MOD cavities performed better in terms of fatigue resistance when CC was performed compared to the same FRC restorations without CC. On the contrary, teeth restored with SFC restorations performed better without CC compared to the ones where SFC was covered. CLINICAL RELEVANCE: In the case of fiber-reinforced direct restorations for MOD cavities in RCT molars, direct CC is recommended when utilizing long continuous fibers for reinforcement, however, should be avoided when only SFC is used for their reinforcement.

A comparative assessment of color stability among various commercial resin composites.

OBJECTIVES: The aim was to evaluate the color stability of six commercial restorative resin composites after being exposed to commonly consumed beverages. Repolishing impact on the stained composite was also assessed. METHODS: One-hundred and fifty disc specimens (8 mm diameter & 3 mm thickness) were prepared from Filtek™ Universal Restorative, SDR flow+, everX Flow, G-ænial A'CHORD, G-ænial Universal Flo and G-ænial Universal Injectable. To assess the color stability in five various beverages, 25 specimens from each material were randomly distributed into five groups (n = 5), according to the utilized staining solution. Group 1: distilled water, Group 2: coffee, Group 3: red wine, Group 4: energy drink, Group 5: coke. The color changes (∆E) for all materials were measured using spectrophotometer at the baseline, after 84 days of staining and after repolishing. Data was collected and analyzed using ANOVA (α = 0.05). RESULTS: Both material type and staining solution had a significant effect on the color stability of specimens (p < 0.05). Compared to other beverages, the color value of the specimens submerged in coffee and wine showed the most statistically significant (p < 0.05) mean ∆E. SDR flow + in coffee and wine presented the highest ∆E when compared to other tested materials (p < 0.05). After staining of the composites, repolishing was successful in lowering the ∆E value. CONCLUSIONS: All the beverages had an impact on the color stability of the tested resin composites, with coffee and wine demonstrating the most significant effects. The variations in color stability varied depending on the specific material utilized. Dentists should possess awareness regarding the chemical interactions that occur between different beverages and various types of resin composites. Additionally, repolishing serves as an effective technique for eliminating surface discoloration in composite restorations.

Fatigue performance of endodontically treated premolars restored with direct and indirect cuspal coverage restorations utilizing fiber-reinforced cores.

OBJECTIVES: The aim of this in vitro study was to investigate the fatigue survival and fracture behavior of endodontically treated (ET) premolars restored with different types of post-core and cuspal coverage restorations. MATERIALS AND METHODS: MOD cavities were prepared on 108 extracted maxillary premolars. During the endodontic treatment, all teeth were instrumented with rotary files (ProTaper Universal) to the same apical enlargement (F2) and were obturated with a matched single cone obturation. After the endodontic procedure, the cavities were restored with different post-core and overlay restorations (n = 12/group). Three groups (A1-A3) were restored with either conventional composite core (PFC; control) or flowable short-fiber-reinforced composite (SFRC) core with/without custom-made fiber posts and without overlays. Six groups had similar post-core foundations as described above but with either direct PFC (B1-B3) or indirect CAD/CAM (C1-C3) overlays. Fatigue survival was tested for all restorations using a cyclic loading machine until fracture occurred or 50,000 cycles were completed. Kaplan-Meyer survival analysis was conducted, followed by pairwise post hoc comparisons. RESULTS: None of the restored teeth survived all 50,000. Application of flowable SFRC as luting-core material with fiber post and CAD/CAD overlays (Group C3) showed superior performance regarding fatigue survival (p < 0.05) to all the other groups. Flowable SFRC with fiber post and direct overlay (Group B3) showed superior survival compared to all other direct techniques (p < 0.05), except for the same post-core foundation but without cuspal coverage (Group A3). CONCLUSIONS: Custom-made fiber post and SFRC as post luting core material with or without cuspal coverage performed well in terms of fatigue resistance and survival when used for the restoration of ET premolars. CLINICAL RELEVANCE: The fatigue survival of direct and indirect cuspal coverage restorations in ET MOD premolars is highly dependent on whether the core build-up is fiber-reinforced or not. The combination of short and long fibers in the form of individualized post-cores seems to offer a favorable solution in this situation.

Shear-bond strength and optical properties of short fiber-reinforced CAD/CAM composite blocks.

The aim of this study was to assess the shear-bond strength (SBS) of resin-luting cement to experimental short fiber-reinforced CAD/CAM composite (SFRC) compared to conventional CAD/CAM (Cerasmart 270), 3D printed (GC TEMP PRINT, Pro3dure GR-17), and laboratory (Gradia Plus) composites. Moreover, translucency parameter values and light transmission were evaluated. For each of the five types of composites, discs were prepared (n = 16/group) and divided into subgroups (n = 8/group) according to surface treatment protocol (hydrofluoric acid or air-particle abrasion). SBS test was performed using universal testing machine until failure, and failure modes were visually analyzed. Translucency parameter and curing-light transmission values through 1, 2, and 3 mm thickness were quantified using spectrophotometry and the MARC resin calibrator, respectively. Scanning electron microscopy (SEM) was used to examine the CAD/CAM composites after surface treatment. Composite type and surface treatment had a significant effect on SBS. Laboratory composite showed the highest SBS value (22.4 MPa). Cerasmart 270 exhibited higher translucency parameter values (19.8, 11.0, 5.0) than SFRC (14.5, 5.2, 1.6) at the three composite thicknesses tested. Air-particle abrasion was more effective in enhancing SBS than acid etching. Experimental SFRC CAD/CAM composite showed higher SBS values than Cerasmart 270. For all composites, translucency parameter values and light transmission decreased as thickness increased.

Fatigue failure load of immature anterior teeth: influence of different fiber post-core systems.

The aim was to explore the fracture-behavior, survival and marginal-microgaps within the root-canal of immature anterior teeth restored with different fiber-reinforced post-core composites (FRCs). 180 bovine-incisors were randomly divided into 6 groups (n = 30). One group served as control (group 6). The rest of the teeth were prepared to an internal diameter of 1.6 mm and the apex was sectioned. After application of an MTA-plug, teeth were restored with FRC materials: Group 1: Bioblock technique with short fiber-reinforced composite (SFRC); Group 2: Bioblock technique with flowable SFRC; Group 3: Individually-made FRC post; Group 4: Conventional FRC post; Group 5: dual-cure core build-up composite. After restorations were completed, teeth (n = 5/group) were sectioned and then stained. Specimens were viewed under a stereo microscope and the percentage of microgaps within the root-canal was calculated. Fatigue-survival was measured using a cyclic-loading testing machine in the rest of the specimens. Flowable SFRC application in the root-canal (Group 2) did not differ from intact-teeth regarding fatigue-survival (p > 0.05). The rest of the groups produced significantly lower survival (p < 0.05) compared to intact-teeth. Post/core restorations made from conventional FRC post (Group 4) exhibited a high number of microgaps (38.3%) at the examined interphase in the root-canal. The restoration of immature incisors with the use of flowable SFRC as post-core material displayed promising performance in a matter of fatigue-resistance and survival.

Incorporation of cellulose fiber in glass ionomer cement.

This study investigated the effect of discontinuous cellulose microfibers with various loading fractions on selected physical properties of glass polyalkenoate (glass ionomer) cement (GIC). Fiber-reinforced GIC (Exp-GIC) was prepared by adding discontinuous cellulose microfiber (with an average length of 500 µm) at various mass ratios (1, 2, 3, 4, and 5 mass%) to the powder of conventional GIC (GC Fuji IX) using a high-speed mixing device. Fracture toughness, work of fracture, and compressive strength were determined for each experimental and control material. The specimens (n = 6) were wet stored (37°C for 1 d) before testing. A scanning electron microscope equipped with an energy dispersive spectroscope was used to examine the surface of fibers after treatment with cement liquid. Data were analyzed using ANOVA. The Exp-GIC (5 mass%) specimen had statistically significantly higher fracture toughness (0.9 MPa.m1/2 ) than unreinforced material (0.4 MPa.m1/2 ). On the other hand, Exp-GIC with 1 mass% displayed the highest compressive strength (116 MPa) among all tested groups. The use of discontinuous cellulose microfibers with conventional GIC matrix considerably increased the toughening performance compared with the particulate GICs used.

Fracture resistance and marginal gap formation of post-core restorations: influence of different fiber-reinforced composites.

OBJECTIVES: The aim was to explore the fracture behavior and marginal gap within the root canal of endodontically treated (ET) premolars restored with different fiber-reinforced post-core composites (FRCs). Further aim was to evaluate the composite curing at different depths in the canal. MATERIALS AND METHODS: Eighty-seven intact upper premolars were collected and randomly divided into six groups. After endodontic procedure, standard MOD cavities were prepared and restored with their respective fiber-reinforced post-core materials: group 1: prefabricated unidirectional FRC-post + conventional composite core; group 2: prefabricated unidirectional FRC-post + short fiber composite (SFRC) core; group 3: individually formed unidirectional FRC-post + conventional composite core; group 4: randomly oriented SFRC directly layered as post and core; group 5: individually formed unidirectional FRC + randomly oriented SFRC as post and core. After restorations were completed, teeth (n = 3/group) were sectioned and then stained. Specimens were viewed under a stereo microscope and the percentage of microgaps within the root canal was calculated. Fracture load was measured using universal testing machine. RESULTS: SFRC application in the root canal (groups 4 and 5) showed significantly higher fracture load (876.7 N) compared to the other tested groups (512-613 N) (p < 0.05). Post/core restorations made from prefabricated FRC-post (group 1) exhibited the highest number of microgaps (35.1%) at the examined interphase in the root canal. CONCLUSIONS: The restoration of ET premolars with the use of SFRC as post-core material displayed promising performance in matter of microgap and load-bearing capacity. CLINICAL SIGNIFICANCE: Fracture resistance of ET premolar restored by bilayered composite restoration that includes both SFRC as post-core material and surface conventional resin seems to be beneficial.

Effect of interface surface design on the fracture behavior of bilayered composites.

This study aimed to evaluate the effect of different interface designs on the load-bearing capacity of bilayered composite structures (BLS). Cylindrical specimens of BLS were prepared from base composite of 3.5 mm thickness and surface composite of 1.5 mm thickness (n = 80). Two different base composites - flowable bulk-fill (FBF) [smart dentin replacement (SDR)] and short fiber-reinforced (FRC) (everX Posterior) - were evaluated, and conventional composite (G-aenial Posterior) was used as the surface layer. Four different interface designs were used: (i) pyramidal; (ii) mesh; (iii) linear grooves; and (iv) flat surface (control). Three-dimensional printed molds were fabricated to standardize the interface design between the surface and the base composites. The specimens were then statically loaded with a steel ball until fracture using a universal testing machine. Fracture types were classified into catastrophic, complete, and partial bulk. ANOVA revealed that both the material and the interface design had a statistically significant effect on the load-bearing capacity. Flowable bulk-fill showed lower mean load-bearing capacity than FRC in all the interface designs tested, except for the flat surface design. Fracture analysis showed that FRC demonstrated up to 100% partial bulk fractures with the pyramid interface design, but no incidence of catastrophic bulk fracture. By contrast, FBF demonstrated up to 84.6% and 40% catastrophic bulk fractures with the flat interface design but no incidence of partial bulk fracture. Consequently, the interface designs studied enhanced the fracture behavior of BLS.

Characterization of a new fiber-reinforced flowable composite.

This study aimed to evaluate certain physical properties including surface wear of a new experimental short fiber-reinforced flowable resin composite (SFRC) in comparison with different commercial flowable bulk fill resin composites (SDR, Tetric EvoFlow Bulk Fill, Filtek Bulk Fill Flowable and Estelite Bulk Fill Flow). The following properties were examined according to ISO standard: flexural strength, flexural modulus, fracture toughness, water sorption, volumetric shrinkage, and depth of cure. Degree of conversion (DC%) was determined by FTIR spectrometry. A wear test was conducted with 15000 chewing cycles using a dual-axis chewing simulator. Wear depth was measured by a three-dimensional (3D) noncontact optical profilometer. Scanning electron microscopy was used to evaluate the microstructure of SFRC. Data were statistically analyzed with analysis of variance ANOVA (p = 0.05). SFRC exhibited the highest fracture toughness (2.8 MPa m1/2) and flexural strength (146.5 MPa) values (p < 0.05) and the greatest depth of cure (5 mm) and lowest wear depth (18.2 µm) among the flowable bulk fill materials tested. SDR showed the lowest volumetric shrinkage percentage (2.9%), while the other resin composites had comparable volumetric shrinkage values (p > 0.05). The new short fiber-reinforced flowable resin composite differed significantly in its measured fracture toughness compared to the tested flowable bulk fill resin composites.

Fracture behavior of root-amputated teeth at different amount of periodontal support - a preliminary in vitro study.

BACKGROUND: The purpose of this study was to evaluate the effect of the amount of periodontal support on the fracture resistance of root-amputated maxillary molar teeth restored with either direct class. I. restorations or class II. mesio-occluso-distal (MOD) indirect overlay restorations with cuspal coverage. METHODS: Sixty sound maxillary first molars were collected and randomly divided into four groups. In Groups 1 and 2, MOD cavities were prepared and all cusps were reduced by 2 mm, whereas in Group 3 and 4, only a conservative Class I. cavity was prepared. Subsequently, root canal treatment was performed and the mesio-buccal roots were amputated. Groups 1 and 2 were restored with indirect composite overlay, while Groups 3 and 4 received direct composite fillings. After restoration, teeth were embedded as follows: Groups 1 and 3: normal bone level, Groups 2 and 4: furcation involvement. The specimens were submitted to static fracture resistance testing. Fracture thresholds and fracture patterns were measured and evaluated. RESULTS: Group 1 had the highest fracture resistance (2311,6 N) among the restored groups and showed statistically significant difference compared to Group 2 (p = 0.038) and Group 4 (p = 0.011). There was no statistically significant difference in terms of fracture resistance between the rest of the groups. In terms of the fracture patterns, Group 3 was characterized by the highest percentage (60%) of mostly favorable fractures, while the rest of the groups showed predominantly unfavorable ones. CONCLUSIONS: The amount of periodontal support seems to influence the fracture resistance of root-amputated and restored maxillary molars.

Influence of increment thickness on dentin bond strength and light transmission of composite base materials.

OBJECTIVES: Bulk-fill resin composites (BFCs) are gaining popularity in restorative dentistry due to the reduced chair time and ease of application. This study aimed to evaluate the influence of increment thickness on dentin bond strength and light transmission of different BFCs and a new discontinuous fiber-reinforced composite. MATERIALS AND METHODS: One hundred eighty extracted sound human molars were prepared for a shear bond strength (SBS) test. The teeth were divided into four groups (n = 45) according to the resin composite used: regular particulate filler resin composite: (1) G-ænial Anterior [GA] (control); bulk-fill resin composites: (2) Tetric EvoCeram Bulk Fill [TEBF] and (3) SDR; and discontinuous fiber-reinforced composite: (4) everX Posterior [EXP]. Each group was subdivided according to increment thickness (2, 4, and 6 mm). The irradiance power through the material of all groups/subgroups was quantified (MARC® Resin Calibrator; BlueLight Analytics Inc.). Data were analyzed using two-way ANOVA followed by Tukey's post hoc test. RESULTS: SBS and light irradiance decreased as the increment's height increased (p < 0.05), regardless of the type of resin composite used. EXP presented the highest SBS in 2- and 4-mm-thick increments when compared to other composites, although the differences were not statistically significant (p > 0.05). Light irradiance mean values arranged in descending order were (p < 0.05) EXP, SDR, TEBF, and GA. CONCLUSIONS: As increment thickness increased, the light transmission decreased for all tested resin composites. Discontinuous fiber-reinforced composite showed the highest value of curing light transmission, which was also seen in improved bonding strength to the underlying dentin surface. CLINICAL RELEVANCE: Discontinuous fiber-reinforced composite can be applied safely in bulks of 4-mm increments same as other bulk-fill composites, although, in 2-mm thickness, the investigated composites showed better performance.

Influence of increment thickness on light transmission, degree of conversion and micro hardness of bulk fill composites.

This study evaluated characteristics of light transmission, degree of monomer conversion and surface microhardness of bulk fill, conventional and fiber-reinforced resin based composites (RBCs) through different incremental thicknesses of resin composite. Working hypotheses was that there are differences in transmission of blue light through RBCs of different kinds and that the thickness of the increments influence the degree of monomer conversion of RBCs. Six bulk fill, three conventional nanohybrid, one short fiber reinforced and one flowable RBCs were evaluated. For each material, four different incremental thicknesses (1, 2, 3 and 4 mm) were considered (n = 5). The specimens were prepared in cylindrical Teflon molds that are open at the top and the bottom sides and cured for 40 s by applying the curing unit. After curing process, the specimens were ground with a silicon carbide paper with a grit size of 1200 and 4000, and then stored dry at 37 °C for 24 h. Light transmission, degree of monomer conversion, surface microhardness were measured and data were analyzed using ANOVA (p = 0.05). There were differences in light transmission of resin composites of various types and brands. Low-viscous bulk fill and short fiber-reinforced RBCs presented higher light transmission compared to resin composites of higher viscosity. Reduced light transmission and lower surface microhardness and DC % at bottom side of the specimen suggests that more attention needs to be paid to ensure proper curing of the resin composite in deep cavities.

Mechanical properties, fracture resistance, and fatigue limits of short fiber reinforced dental composite resin.

STATEMENT OF PROBLEM: Cycling masticatory loads decrease the strength of particulate filler composites (PFCs) and initiate the failure process by fatigue. The life expectancy of a composite resin restoration under stress remains difficult to predict. PURPOSE: The purpose of this study was to determine the fracture resistance and the compressive fatigue limits (CFL) of anterior crown restorations made of a short-fiber reinforced composite resin (SFC), to investigate selected mechanical properties of the material following standard test methods, and to observe their correlation with the CFL. MATERIAL AND METHODS: Specimens (n=10) were fabricated either from SFC (everX Posterior, GC Corp) or PFC (G-ænial anterior, GC Corp). The properties investigated were flexural strength (FS), compression strength (CS), diametral-tensile strength (DTS), and single-edge-notched-bend fracture toughness (FT) following ISO standards. Fracture resistance was determined by static load (n=10) and the CFL at 10000 cycles was determined using a staircase approach (n=20), both on anterior composite resin crowns. The results were analyzed with 1-way ANOVA (α=.05) or 2-way ANOVA (α=.05) followed by a Tukey B post hoc test and the Pearson-correlation analysis. RESULTS: The SFC crowns had higher fracture resistance (954 ±121 N) than the PFC crowns (415 ±75 N) (P<.001) and higher CFL (267 ±23 N) than the PFC crowns (135 ±64 N) (P<.001). SFC revealed also higher FT (2.6 ±0.6 MPa·m(1/2)) than the PFC (1.0 ±0.2 MPa·m(1/2)) (F=69.313, P<.001). A significant correlation was observed only between the FT and the CFL (r(2)=0.899; P<.001). CONCLUSIONS: SFC crowns showed good performance under static and fatigue loading. FT was the only in vitro test method that filtered as a clinically relevant parameter.

Oxygen inhibition layer of composite resins: effects of layer thickness and surface layer treatment on the interlayer bond strength.

An oxygen inhibition layer develops on surfaces exposed to air during polymerization of particulate filling composite. This study assessed the thickness of the oxygen inhibition layer of short-fiber-reinforced composite in comparison with conventional particulate filling composites. The effect of an oxygen inhibition layer on the shear bond strength of incrementally placed particulate filling composite layers was also evaluated. Four different restorative composites were selected: everX Posterior (a short-fiber-reinforced composite), Z250, SupremeXT, and Silorane. All composites were evaluated regarding the thickness of the oxygen inhibition layer and for shear bond strength. An equal amount of each composite was polymerized in air between two glass plates and the thickness of the oxygen inhibition layer was measured using a stereomicroscope. Cylindrical-shaped specimens were prepared for measurement of shear bond strength by placing incrementally two layers of the same composite material. Before applying the second composite layer, the first increment's bonding site was treated as follows: grinding with 1,000-grit silicon-carbide (SiC) abrasive paper, or treatment with ethanol or with water-spray. The inhibition depth was lowest (11.6 µm) for water-sprayed Silorane and greatest (22.9 µm) for the water-sprayed short-fiber-reinforced composite. The shear bond strength ranged from 5.8 MPa (ground Silorane) to 36.4 MPa (water-sprayed SupremeXT). The presence of an oxygen inhibition layer enhanced the interlayer shear bond strength of all investigated materials, but its absence resulted in cohesive and mixed failures only with the short-fiber-reinforced composite. Thus, more durable adhesion with short-fiber-reinforced composite is expected.

Biomechanics, Bioactive and Biomimetic philosophy in restorative dentistry ̶ Quo vadis?

INTRODUCTION: In recent years, restorative dentistry has embraced various techniques, including direct, semi-direct, and indirect restorations, to address the replacement of lost tooth tissue. The focus has been on integrating the principles of Biomechanics, Bioactivity, and Biomimicry (3-Bio) as key drivers behind these innovations. METHODS: The aim of this article is to provide a concise overview of three important aspects of restorative dental materials: biomechanics, bioactivity and biomimetics. Further, the aim is to provide readers with relevant information on the 3-Bio concept, offering insights in to the innovative approaches shaping modern restorative dentistry. RESULTS: Developing restorative materials with interactive properties aligned with the 3-Bio concept poses a significant challenge. Currently, dentistry lacks a comprehensive system in this regard. The development of dental materials based on the 3-Bio concept could potentially elicit positive mechanical and biological responses in targeted tooth tissues. CONCLUSION: Assessing several parameters through a battery of in vitro and in silico assays could help in tailoring the different aspects of the 3-Bio concept, spanning from bioactivity to biomimetics via biomechanics. This approach could allow the prediction and translation of the clinical performance of the assessed restorative materials. CLINICAL SIGNIFICANCE: The findings of this opinion article highlight that the development of restorative materials aligned with the 3-Bio concept could enhance the management of dental defects and extend the longevity of bonded restorations, thereby improving patient care through tissue preservation. More collective efforts between clinicians, researchers, and even industrial partners are required to fully understand the correlation between bioactive behavior, biomechanical limitations, and biomimetics to provide suitable restorative materials for specific clinical applications.